1. Field of Invention
The invention relates to a safety insert for extra-corporeal circuits, in particular a seat formed in the insert for receiving a pipe.
2. Description of the Prior Art
In therapeutic treatment which requires an extra-corporeal circulation system, such as haemodialysis, the arterial and venous pressure in the extra-corporeal circuit must be constantly monitored. This is achieved in a manner known per se by means of pressure transducers connected to the main circuit via suitable branch pipes. In an equally known manner, a safety insert or transducer protector is positioned between the pipe and the pressure transducer in order to avoid any possible contact between the patient's blood and the machine (artificial kidney). In fact, the extra-corporeal circuit is made of disposable material, while the artificial kidney as a whole must, of necessity, be continuously reused.
The transducer protector is formed, in a manner known per se, by means of two plastic half-shells enclosing between them a hydrophobic gas permeable membrane. Each of the two half-shells comprises a tubular connector. A first tubular connector is designed to be connected to the branch pipe, while the other tubular connector is designed to be connected to the pressure transducer.
In particular, during assembly of the disposable material, the branch pipe is dipped in a solvent and manually inserted inside the first tubular connector of the transducer protector so as to obtain secure bonding together of the two parts.
This solution, although widely used, is not defect-free. In fact, the use of an excessive quantity of solvent may easily result in the contamination of the hydrophobic membrane and cause consequent damage thereto. Obviously, the correct assembly procedure requires the removal of any excess solvent in order to limit the possibility of this occurring.
The structure of the known transducer protectors therefore has a minimum safety margin which is essentially dependent on the procedure and the degree to which it is complied with by the operator.
The Applicant expressly conducted a specific series of tests to investigate these problems. In particular, 194 pairs of pipes and transducer protectors of the known type were assembled. With each of the 194 pairs the aforementioned assembly operation was systematically conducted in a manner which deliberately did not comply with the procedure. The result of the tests was that the failure to remove the excess solvent resulted in contamination of the membrane in as many as 106 of the 194 cases, i.e. in more than 54% of the total number of cases. The above therefore shows how the transducer protector of the known type proves to be reliable only if used in strict compliance with the procedures indicated. It would therefore be highly desirable to provide a transducer protector able to ensure a greater safety margin, in particular, a safety margin able to prevent contamination of the membrane even in the case where the operator commits errors during application of the procedure or in the case where he/she is unable or considers it unnecessary to adhere rigorously to the procedure.
Safety inserts of the type considered above are described in detail in the documents EP 0 652 018, EP 1 097 725 and EP 0 878 628.